The present invention relates to a device for measuring the level of a metal bath underneath a slag layer and in metallurgical vessel.
German printed patent application No. 29 37 353 describes a device, i.e. probe or sampling device, for measuring the depth of the level of molten metal underneath slag cover. This type of device is deemed advantageous particularly from the point of view of the principle of operation. Therefore, in practice with measuring result was deemed reliable and particularly it has been the common belief that the values ascertained by means of such a device depict accurately the actual conditions in the vessel. It was found, however, that upon measuring the bath level during insertion of the lance holding the probe, errors arose. These errors may quite possibly be attributed to a coating of the electrodes with the slag as the probe traverses the slag layer. This would means that the direct engagement of the electrodes with the steel in the bath is delayed because that coating has to melt off in the bath before the steel can engage the electrodes. This delay occurs upon insertion of the probe and simulates a lower level of the metal bath than is actually present.
In order to avoid the aforementioned problem, it has been tried to cover the electrodes with sheet metal caps which melt on contact with the metal bath and the level is actually ascertained during retraction of the probe. However, comparative measurements indicate that this method is likewise not free from errors whereby particularly the magnitude of the error is dependent upon the speed of lance motion.